Self supporting optical document scanning system

ABSTRACT

A document scanning system is disclosed which utilizes a scan carriage mounted on guide rails which are connected between novel support members. The support members are mounted at one location only to a fixed base support. The guide rails do not require mounting to a side frame structure; the support structure providing the stability usually provided by the sides of a frame. The guide rails are inherently stable and provide the support for the scan load components. The second embodiment of the invention uses a single guide rail to support the optical system rather than plural guide rails.

BACKGROUND AND PRIOR ART STATEMENT

This invention relates to an optical document scanning system for adocument reproduction machine and, more particularly, to an improvedassembly for supporting the optical components used during the documentscan operation.

In the document reproduction art, an original document to be reproducedis typically placed on a stationary platen and illuminated by aincremental line-scanning optical system. Reflected light rays from thedocument travel along an optical path and are projected by a lens on toa photosensitive image member. The latent image of the document formedon the image member is then developed by appropriate marking material,and the developed image transferred to a record medium such as paper.Various types of scan mechanisms are known in the art, but the mostwidely used utilize a pair of guide rails which are mounted in aparallel plane beneath the document platen. The scanning components aremounted on one or more movable scan carriages which are driven by acable arrangement to run back and forth beneath the platen and supportedby the guide rails. Examples of such prior art scan systems employing anelongated illuminated lamp and scan mirrors to scan/illuminate thedocument are shown in U.S. Pat. Nos. 4,367,945, 4,155,641 and 4,603,963.The document to be reproduced may also be scanned by a raster inputscanner (RIS), typically a CCD sensor array. The RIS type scanner issupported for movement beneath the document platen and is moved in thescan, re-scan direction by a scan assembly basically similar to the onesused in the above-identified patents. U.S. Pat. No. 4,500,197 disclosesa RIS type scan system. The prior art scanning system can becharacterized as being secured to, and supported by, the sides of aframe assembly. Thus, U.S. Pat. No. 4,367,945 to Abe discloses ascanning support structure for an electrostatic copying machinecomprising a guide rail 22 and a guide rod 23 which together support andabsorb the loads of two movable carriages 12 and 14, while beingsupported by frame members 20 and 21. U.S. Pat. No. 4,155,641 to Sagaraet al. discloses a scanning apparatus comprising three parallel guiderods 52, 53, and 54, attached to a beam member 20, which support theloads imposed by two movable optical scanning carriages 50 and 51. U.S.Pat. Nos. 4,603,963 to Hinton et al., and 4,710,017 to Watanabe et al.are references which disclose scanning systems comprising a pair offrame supported parallel guiding members which absorb the shock andloads of a moving carriage apparatus within an electrostatic copyingmachine. U.S. Pat. No. 4,500,197 to Dannatt discloses a supportstructure for a flat bed scanner comprising a pair of parallel,elongated guide rods 55 and 62 fixed to left and right end plates 14 and16, which form rigid support for the loads imposed by a movable RISoptical scanning carriage assembly 12.

SUMMARY OF THE INVENTION

In each of the above-prior art systems, which are representative of theknown scan systems, the scan components mounted on the guide railsrequire integral connection to a formal frame structure with the framestructure providing the support for the mass of the guide rails andoptical scan components. The requirement for a frame structure increasesthe cost of the scan system, while the mounting interconnection betweenthe scan components and the frame sides increases the system complexity.According to one aspect of the present invention, a scan assembly ismounted in a frameless environment by making efficient use of theinherent stiffness of the guide rails to support the scanningcomponents. More particularly, the guide rails are mounted with anassembly which is secured to a base support. Cable tension and the scanload components are located at the center line of the guide shafts, theguide shafts now providing all the needed support formerly supplied bythe side walls of the frame member. Still more particularly, theinvention relates to an imaging system for incrementally illuminating adocument in an object plane and transmitting reflected incrementalimages to a photosensitive image member, an illumination/scan systemcomprising; a scan carriage movable in a reciprocal path along at leastone guide rail which extends in a plane beneath and parallel to saidobject plane, at least one support structure for supporting saidcarriage, said support structure extending between the start and end ofscan positions, said support structure further including a capstanassembly rotatingly driven by a drive shaft, and further including adrive cable wrapped around said capstan assembly and connected at theother end of said carriage, the scan carriage being driven along saidreciprocal path by said drive cable and wherein said capstan assemblyand cable are located along the center line of said guide rails, theguide rails providing the support for the scanning components.

IN THE DRAWINGS

FIG. 1 is a schematic side view of a document reproduction systemutilizing the RIS type scanner mechanism support structure of thepresent invention.

FIG. 2 is a perspective view of the optical scanning mechanism of FIG.1.

FIG. 3 is a top plan view of the scanning mechanism of the opticalscanning mechanism of FIG. 1.

FIG. 4 is a side plan view of the optical scanning mechanism of FIG. 1.

FIG. 5 is a top plan view of a second embodiment of an optical scanningsystem of the present invention utilizing only one scan supportstructure.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, raster input scanner assembly is locatedbeneath a document platen 6. Assembly 4 includes a scanning arraycarriage 8 supported for reciprocating scanning movement by two supportrails 10 (FIG. 2). Rails 10 extend parallel to the platen and arelocated between support structures described below. Scanning arraycarriage 8 is supported on support member 12 which is movingly mountedon rails 10 by bearings or bushings at the frictional interface.Photosensor array 14, which may be a linear array of photosensitivescanners such as CCD's or photodiodes which sense light reflected from adocument during an integration period, is supported on member 12. Thephotosensors develop a charge indicative of the amount of lightdetected. In a preferred embodiment of the invention, the array maycomprise several smaller arrays butted at their ends to form an unbrokenarray as, for example, the arrays described in U.S. Pat. No. 4,604,161to Araghi.

A document 28, placed on platen 6, is illuminated by a lamp assemblysupported on member 12 and including lamp 16. The lamp, when energizedby a power supply (not shown), directs light towards the document to bescanned. Light from the illuminated document is reflected to lens 18,comprising a bundle of image transmitting fiber lenses produced underthe tradename of "SELFOC" by Nippon Sheet Glass Company Limited. Lens 18directs light reflected from the document to scanning array 14. Adjacentto the portion of lens 18 closest to the document is a reflector 20,extending generally towards the document which may be advantageouslyprovided with a light reflecting concave surface to further aid indirecting light from lamp 16 to illuminate the document. It will, ofcourse, be appreciated that other optical and illuminating systems maybe used to illuminate and direct light from the document to the scanningarray. In a conventional copying operation, assembly 8 is driven fromposition S₀ to position S₁. As the scanning assembly is moved across theplaten, the sensors of the sensor array 14, are repeatedly exposed toincremental areas of the document being copied, producing chargeinformation indicative of the image on the document for use inassimilating an electronically stored image of the document. Electricaloutput signals from array 14 are used to control the operation of araster output scanner (ROS) unit 21. ROS 21 forms a modulated imagelight pattern on the charged surface of a photoreceptor drum 22 atexposure station B. As a result of this imaging operation the charge onthe drum surface is selectively dissipated in the light exposed regions,thereby recording the original input scene information on thephotoconductive plate surface in the form of a latent electrostaticimage. Next, in the direction of drum rotation, the image bearing platesurface is transported through a development station C wherein the tonermaterial is applied to the charged surface thereby rendering the latentelectrostatic image visible. The now developed image is brought intocontact with a support sheet 23 such as paper or the like, within atransfer station D wherein the toner image is electrostaticallyattracted from the photoconductive plate surface to the contacting sideof the support sheet. Station E represents a mechanism for cleaningtoner from the drum surface. station A recharges the surface of drum 22.Control of the RIS and ROS operation the various xerographic stations isaccomplished by an on-board microprocessor controller (not shown) of thetype commonly used to control light lens and raster scanners.

The optical system will now be described with further detail and withadditional reference to FIGS. 2-4. In the base mode of operation, thecopier is operated to faithfully produce a copy of a document 28 whichis placed image side down upon a platen 6. This is accomplished by scancarriage 8 moving in a scan path parallel to the platen. The carriage 8is adapted to ride on scan rails 10 along teflon pads 30, 32 whichslidingly contact the rails along the top and side surfaces,respectively. One end of each rail 10 is located in bores 34 formed atthe ends of support structure 36. The other ends of rail 10 are locatedin yokes 38. The yokes also support idler pulleys 40. A support 42mounted to a base plate 44 by screws 46 serves to clamp the yoke andidler pulley into position. Support structure 36 is secured to a baseplate 44 in similar fashion. Structure 36, supports a capstan pulleymember 48. Pulley 48 terminates at the non-drive end in a bearingassembly 50. The other drive end terminates in an end shaft 52 which isdriven by motor 54 via a timing belt 55. Wrapped around the ends ofcapstan pulley 48 are drive cables 56. Each drive cable is adapted to bealigned along the center of their respective rails 10. Springs 58 applytension to cables 56. One end of cables 56 are wrapped around capstanpulley 48 and driven therearound while the other end terminates inbracket 60 secured to the drive carriage. In operation, the drive motor54, in response to copy signals, drives capstan pulley 48 which in turndrive cables 56 causing carriage 8 to move in a left-to-right (scan) andright-to-left (rescan) direction. The CCD array 18 scans reflected lightfrom document 28, and generates electrical signals which areperiodically transferred to ROS 21. ROS 21 is thus activated toselectively expose the surface of drum 22 forming the latent imagethereon. According to the principle of the present invention, and asdescribed above, the support structure 36 is secured solely to a baseplate 44 with the guide rails firmly secured at both ends. The drivecables are mounted along the guide rail center line, hence the cabletension, the scan loads of the scan carriage, and the idler pulley areall located along the guide shaft center line. The inherent stiffness ofeach guide rail is thus utilized to absorb the loads of the systemrelieving the necessity of obtaining support from the vertical framemember/platen as in the prior art.

A second embodiment of the invention is shown in FIG. 5. In thisembodiment, carriage 8 is centrally located over a single guide rail 10.Capstan pulley assembly 48' is housed in truncated frame structure 36'.The locating of cable 56 and the securing of structures 36' and 42'correspond to their longer counterpart shown in FIGS. 2-4.

While the invention has been described with reference to the structuredisclosed, it will be appreciated that numerous changes andmodifications are likely to occur to those skilled in the art, and it isintended to cover all changes and modifications which fall within thetrue spirit and scope of the invention.

I claim:
 1. In an imaging system for incrementally illuminating adocument in an object plane and transmitting reflected incrementalimages to a photosensitive image member, an illumination/scan systemcomprising;a scan carriage movable in a reciprocal path along at leastone guide rail which extends in a plane beneath and parallel to saidobject plane, said guide rail secured at its ends to a first and secondsupport structure, said first support structure locating a capstanpulley, and said second support structure locating a yoke and idlerpulley assembly, and further including a drive cable wrapped around saidcapstan assembly and said idler pulley and connected at the other end tosaid carriage, means for rotating the capstan pulley whereby the scancarriage is driven along said reciprocal path by said drive cable andwherein said capstan assembly, idler pulley assembly and cable arelocated along the center line of said guide rails, the guide railsproviding the support for the scanning components.
 2. The imaging systemof claim 1, wherein said imaging system includes means for incrementallyilluminating said document and for transmitting reflected light to alinear photosensor array.
 3. The imaging system of claim 2, wherein thescan carriage is a RIS carriage mounted along a single guide rail.